docs: def _get_stddevs(self, C, stddev_types, rup, imt, num_sites):
          """
          Return standard deviations as defined in eq. 4 and 5, page 744,
          based on table 8, page 744.
          Eq. 5 yields std dev in natural log, so convert to log10
          """
          stddevs = []
          for stddev_type in stddev_types:
              sigma_mean = self._compute_standard_dev(rup, imt, C)
              sigma_tot = np.sqrt((sigma_mean ** 2) + (C['SigmaReg'] ** 2))
              sigma_tot = np.log10(np.exp(sigma_tot))
              stddevs.append(sigma_tot + np.zeros(num_sites))
          return stddevs